Access device routing device and method thereof supporting stateless address configuration communication network

ABSTRACT

The present invention relates to an IPv6-based access device, edge router and method for stainless address configuration for IPv6 user equipment in an Ethernet access network, wherein, the access device adds the relay agent ID indicating the access device itself and the relevant port identifier indicating the user equipment to a router solicitation message sent by the user equipment in the form of a newly defined option, and forwards the message to the relevant edge router; and the edge router configures a dedicated address prefix for the user equipment according to the relay agent ID and port identifier, combines the address prefix, the relay ID and the port identifier into a router response message, and sends the response message to the relevant access equipment indicated by the relay ID; the access device sends a router advertisement message only including the address prefix via the line port indicated by the port identifier to user equipment. By allocating the dedicated address prefix to every data subscriber line for IPv6 service, IPv6 stainless address configuration is achieved to solve the security and scalability problems in the prior art.

FIELD OF THE INVENTION

The present invention relates to an access network, and in particular,to a device and method of implementing address configuration in anaccess network.

BACKGROUND OF THE INVENTION

IPv6 stateless configuration is considered a configuration manner newlydefined in the IPv6 protocol, by which flexible configuration of aterminal can be achieved and plug&play of a terminal device is madepossible.

FIG. 1 shows a schematic view of an access network architecturesupporting IPv6 user equipment, in which there are comprised a pluralityof user equipment (only user equipment 3 is shown for simplicity), anaccess device (or access node) 1 and a router 2. Among them, accessdevice 1 can be a layer 2 device with some layer 3 functionalities. Atypical such device is IPDSLAM (IP Digital Subscriber Line AccessMultiplexer). Router 2 can be an IPv6 protocol-based edge router (IPv6BRAS/Edge Router).

In the standard IPv6 stateless configuration, user equipment 3 firstgenerates a local link transfer address by itself, and then multicasts,by taking the address as a source address, address configurationinformation called router solicitation (RS) via access device 1 to allrouters 2 on the local link. Router 2 responds to the solicitation witha router advertisement (RA) message which contains an aggregate globalunicast transfer address prefix and other relevant configurationinformation. User equipment 3 combines the global address prefix whichit gets via access device 1 from router 2 and an interface identifiergenerated by itself to generate a global address automatically. Andthrough repeated address detection, user equipment 3 can communicatewith other user equipment on the Internet. Using statelessconfiguration, IP addresses of all hosts within a network can be changedwithout manual intervention.

However, IPv6 stateless configuration, which was generated in opennetwork applications, goes on the premise that neighboring nodes trusteach other. Directly applying this mechanism in an access network willcause security and scalability problems of the access network,especially for a layer 2 access device or an enhanced layer 2 accessdevice with some layer 3 functionalities. Detailed description will begiven below.

Applying the standard IPv6 stateless configuration mechanism in anaccess network will cause the following problems:

1. Potential security problem: in stateless configuration, when multipleDSL lines share the same prefix, malicious user equipment could easilyspoof IP addresses by directly getting the advertised prefix. It isalmost impossible for access device 1 to support an anti-spoofing filtersince no address state information has been maintained at access device1.

2. Potential scalability problem: when access device 1 receives a RAfrom edge router 2, it has to relay this RA message to all DSL lineusers. This is because that access device 1 has no knowledge which DSLline the RA message is targeting to. As the number of broadband userskeeps increasing, relaying the RA message to all DSL line ports couldcause certain performance problem which may eventually have side effecton the scalability of access device 1.

In order improve security and scalability, it is preferred that edgerouter 2 advertises a dedicated address prefix to each DSL line.Thus, 1) access device 1 could easily realize an IP addressanti-spoofing filter by inspecting the prefix of a packet's source and2) access device 1 could avoid the scalability problem by only relayingthe RA message from edge router 2 to a particular DSL line.

The technical problem to be solved in the prior art is how to supportsuch configuration of allocating one address prefix for each DSL lineconfiguration in a broadband access network employing a layer 2 accessdevice with some layer 3 functionalities.

In an existing layer 2 access network, both VLAN-based cross-connectedmode and MAC address-based bridge mode can be employed in dataforwarding. For the technical problem described above, one existingsolution is that access device 1 may operate in cross-connected mode,VLAN (virtual local area network) is configured to identify and separatetraffic or information (e.g. RS message) from different DSL lines. AtIPv6-based edge router 2, the RA message containing a particular addressprefix will be only sent to the DSL line identified by a certain VLAN.In cross-connected mode, no modification is needed in access device 1.Here, cross-connect mode means that the user's VLAN information could bemaintained at network side and different customers will not share thesame VLAN identifier.

Since the number of VLAN identifiers is limited (<=1024 VLANs) (anaccess network can support at most 1024 VLANs), it would be impossiblefor an access network to support one VLAN identifier per a DSL line whenthere are a large number of DSL lines in the access network. VLANstacking is an alternative solution to solve the scalability problem ofstandard VLAN solution. By using VLAN stacking, it is possible to scaleup to support 1024*1024 distinct VLANs. Unfortunately, VLAN stacking hasnot been standardized, and thus is not supported by all access devicesand Ethernets.

When access device 1 operates in bridge mode, since DSL line identifierscannot be transferred to network side, edge router 2 cannot allocate aparticular address prefix for each DSL line correctly. Here, bridge modemeans that since the DSL line information of user equipment cannot bemaintained at network side, it is impossible to effectively distinguishdifferent user equipment.

The present invention is proposed to solve the aforesaid problems in theprior art.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a technical solution thatenables an access node in bridge-mode to support one-addressprefix-per-line IPv6 stateless configuration in an access network. Byadding a relay-agent port identifier option in RS and RA messages, anIPv6 edge router can get the ID information of a DSL line and use theinformation to allocate a proper IPv6 address prefix for each DSL user.

The VLAN (or VLAN-stacking) approach realizes one-addressprefix-per-line using Ethernet technology. This requires all Ethernetdevices between the user equipment and the edge router support the VLANmechanism and the access node needs to operate in cross-connect mode.

The present invention realizes one-address prefix-per-line using IPtechnology, i.e., by encapsulating the DSL line ID information into RAand RS messages. This solution allows the access node to operate inbridge mode or one VLAN to be shared between different users. But thissolution requires both the access node and the edge router shouldsupport this RS/RA extension.

According to a first aspect of the present invention, there is provideda method for address configuration in an access device in an IPv6protocol supported communication network, the method comprising:receiving a user solicitation message from user equipment; adding useridentification information identifying the user equipment to the usersolicitation message, to generate a solicitation message to which theuser identification information is added; and sending the solicitationmessage to which the user identification information is added to arouter.

Preferably, the method further comprises the steps of: receiving arouter response message from the router; separating address prefixinformation and the user identification information from the routerresponse message; and sending the address prefix information tocorresponding user equipment in accordance with the user identificationinformation.

According to a second aspect of the present invention, there is providedan access device for address configuration for user equipment in an IPv6protocol supported communication network, the access device comprising:first reception means for receiving a user solicitation message fromuser equipment; message combination means for adding user identificationinformation identifying the user equipment to the user solicitationmessage, to generate a solicitation message to which the useridentification information is added; and first sending means for sendingthe solicitation message to which the user identification information isadded to an edge router.

Preferably, the access device further comprises: second reception meansfor receiving a router response message from the router; messageseparation means for separating address prefix information and the useridentification information from the router response message; and secondsending means for sending the address prefix information tocorresponding user equipment in accordance with the user identificationinformation.

According to a third aspect of the present invention, there is provideda method for address configuration in a routing device of an IPv6protocol supported communication network, the method comprising:receiving a user solicitation message from an access device; separatinguser identification information from the user solicitation message;allocating a user-specific address prefix based on the useridentification information; adding the user-specific address prefix andthe user identification information to a router response message; andsending the router response message to which the user identificationinformation and the specific address prefix are added to the accessdevice.

According to a fourth aspect of the present invention, there is provideda routing device for address configuration for user equipment in an IPv6protocol supported communication network, the routing device comprising:reception means for receiving a user solicitation message from an accessdevice; message separation means for separating user identificationinformation from the user solicitation message; allocation means forallocating a user-specific address prefix based on relay agentidentification (ID) and a port identifier; message combination means foradding the user-specific address prefix, the relay agent identificationand the port identifier to a router response message; and sending meansfor sending the router response message to which user identificationinformation and specific address prefix are added, to the access device.

Compared with the prior art, the present invention achieve statelessaddress configuration for IPv6 service by allocating a dedicated addressprefix for each data subscriber line, thereby solving the security andscalability problem caused by applying the solution of the prior art toan access network directly. It allows an access device to operate inbridge mode when the VLAN (VLAN stacking) is not supported by the accessdevice and an EMAN network or when multiple lines share the same VLAN.Furthermore, the present invention makes no modification to userequipment. User equipment can directly employ the standard IPv6 protocolstack.

BRIEF DESCRIPTION ON THE DRAWINGS

Hereinafter, detailed description will be given to the present inventionwith reference to the accompanying drawings in which like or similarreference numerals denote the same components:

FIG. 1 is a schematic view an IPv6 standard-based layer 2 access networkarchitecture in the prior art;

FIGS. 2A-C are schematic views of a router solicitation message format,a router advertisement message format and a message additional optionformat in the prior art;

FIG. 3 is a schematic view of an option format to which routersolicitation and advertisement messages can be added according to anembodiment of the present invention;

FIG. 4 is a schematic view of stateless address configuration for userequipment in an IPv6 standard-based layer 2 access network architectureaccording to an embodiment of the present invention;

FIG. 5 is a block diagram of an access device implementing addressconfiguration for user equipment in an access network according to anembodiment of the present invention;

FIG. 6 is a flowchart of a method of implementing address configurationfor user equipment in an access device of an access network according toan embodiment of the present invention;

FIG. 7 is a block diagram of a routing device implementing addressconfiguration for user equipment in an access network according to anembodiment of the present invention; and

FIG. 8 is a flowchart of a method of implementing address configurationfor user equipment in a routing device of an access network according toan embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail with reference to theaccompanying drawings and in terms of concrete embodiments. It is to beunderstood that the present invention is not limited to these concreteembodiments.

FIGS. 2A-2B show schematic views of message formats of a usersolicitation message (e.g. router solicitation (RS) message) from userequipment 3 shown in FIG. 1 and a router response message (e.g. routeradvertisement (RA) message) from router 2 shown in FIG. 1. Both of thesetwo messages belong to the IPv6 neighbor discovery protocol and areencapsulated in an ICMPv6 packet.

As shown in FIG. 2A, in the RS message, the 1^(st) byte is used forindicating type; the 2^(nd) byte is used for indicating code; the3^(rd)-4^(th) bytes are checksum; the 5^(th)-8^(th) bytes are reservedbytes; and subsequent bytes are options.

As shown in FIG. 2B, in the RA message, the 1^(st) byte is used forindicating type; the 2^(nd) byte is used for indicating code; the3^(rd)-4^(th) bytes are checksum; the 5^(th) byte is Cur Hop Limit; inthe 6^(th) byte, the 1^(st) bit denotes M, the 2^(nd) bit denotes O, andthe 3^(rd)-8^(th) bits are used for reservation; the 7^(th)-8^(th) bytesdenote router lifetime; the 9^(th)-12^(th) bytes denote reachable time;the 13^(th)-16^(th) bytes denote retransmission timer; and subsequentbytes are options.

Formats of options in the RS/RA message are as follows:

IPv6 Neighbor Discovery messages (including RS and RA messages) includezero or more options, some of which may appear multiple times in thesame message. All options are of the form shown in FIG. 2C:

wherein,

Type: the type is an 8-bit identifier. The RFC 2461 standard has definedthe type of option as shown in Table 1:

TABLE 1 Option Name Type Source Link-Layer Address 1 Target Link-LayerAddress 2 Prefix Information 3 Redirected Header 4 MTU (MaximumTransmission Unit) 5

Length: 8-bit unsigned integer. The length of the option (including thefields of type and length) is in units of 8 bytes. The value 0 isinvalid. Access device 1 must discard an ND packet that contains anoption with the value 0 of length.

As mentioned previously, there are 5 option types defined in the RFC2461 standard. In order to implement the present invention, we propose anew option type, the format of which is as shown in Table 3:

Option Name Type Relay Agent Option 6

A concrete message format thereof is as shown in FIG. 3, wherein,

Type: 6

Length: 3 (in units of 8 bytes)

Link Identifier This field uniquely identifies a line (port) under anaccess device. In a DSL access network, the MAC address of each DSL lineport can be used as the identifier. If the DSL line port does not have aMAC address, any other local unique layer 2 identifier can be used bythe access node as the identifier.

Relay Agent ID: This field uniquely identifies an RS/RA message relayagent (i.e., an access device). In an IPv6 access network, this filedcan employ the IPv6 address (or any other layer 2 or 3 identifier) ofthe access node used by the service provider for the purpose of networkmanagement.

FIG. 4 is a schematic view of RS/RA solutions for IPv6 statelessconfiguration in an IPv6-based communication network which employsEthernet access device (access node) 1 with some IP layerfunctionalities.

FIG. 4 shows RS/RA agent solutions for layer 2 Ethernet access device(access node) 1 with some layer 3 (IP layer) functionalities so as tosupport IPv6 stateless configuration.

Specifically, FIG. 4 shows one (IPv6 protocol supported) user equipment3, one access device (Ethernet access device with some IP layerfunctionalities) 1 and one routing device (e.g. IPv6 edge router) 2.

First, user equipment 3 sends a user solicitation message (e.g. a routersolicitation (RS) message defined in RFC 2461) to access device 1.

Then, access device 1 adds to the RS message user identificationinformation for identifying the user, which contains the relay agent IDrepresenting access device 1 and the port identifier corresponding touser equipment 3. Access device 1 sends to routing device 2 the RSmessage to which the user identification information was added.

Routing device 2 separates the user identification message (includingrelay agent ID of access device 1 and the port identifier correspondingto user equipment 3) from the received RS message, allocates aparticular address prefix (e.g. IPv6 address prefix) based on the relayagent ID and the port identifier, and contains the information (therelay agent ID, the port identifier and the corresponding particularaddress prefix) in a router response (e.g. a router advertisement (RA)message defined in RFC 2461). As shown in FIGS. 2 and 3, in RS and RAmessages defined in RFC 2461, option 3 contains the address prefixinformation, and option 6 contains the relay agent ID and the portidentifier. Subsequently, routing device 2 sends the RA message to theaccess device 1 corresponding to the relay agent ID.

Access device 1 separates from the RA message option 3 which containsthe particular address prefix information and option 6 which containsthe relay agent ID and the port identifier. Based on the relay agent IDand the line port which the port identifier indicates, and after option6 is removed from the RA message, the RA message from which option 6 wasremoved is sent to user equipment 3 via the line port which the portidentifier represents.

As shown in FIGS. 2, 3 and 4, by adding to RS/RA the relay agent ID ofaccess device 1 and the port information corresponding to the DSL line(e.g. as shown in FIGS. 2-3, a new option 6 is added to the RS/RAmessage), routing device 2 (e.g. edge router) can allocate a dedicatedaddress prefix for each user equipment 3 (or DSL), and access device 2can avoid the scalability problem which might be caused by flooding theRA message to all DSL lines, and implement pre-prefix-IP address-basedanti-spoofing filter (security).

FIG. 5 shows an access device 1 implementing address configuration foruser equipment in an IPv6 protocol-based communication network accordingto an embodiment of the present invention, which comprises firstreception means 11, message combination means 12, first sending means13, second reception means 14, message separation means 15, and secondsending means 16.

First reception means 11 is for receiving a user solicitation message(e.g. a router solicitation (RS) message defined in RFC 2461) from userequipment.

Message combination means 12 is for adding user identificationinformation to the user solicitation message, wherein the useridentification information may contain relay agent ID representing theaccess device 1 and a port identifier corresponding to the userequipment (or DSL).

First sending means 13 is for sending the user solicitation message, towhich the user identification information was added, to a routing device(e.g. edge router).

Second reception means 14 is for receiving a router response message(e.g. a router advertisement (RA) message defined in RFC 2461) from therouting device, which RA message contains user identificationinformation (may contain a port identifier only or relay agent ID and aport identifier) and a particular address prefix (e.g. IPv6 addressprefix) corresponding to the user equipment.

Message separation means 15 is for separating from the router responsemessage the user identification information and the particular addressprefix information. As described previously, the user identificationinformation at least includes a port identifier for identifying the userequipment (or DSL).

Second sending means 16 is for, based on the user identificationinformation, sending the particular address prefix information via aport indicated by the port identifier to the corresponding userequipment.

Preferably, access device 1 is a layer 2 access device with some layer 3functionalities, and more preferably, is an Ethernet access device.

Preferably, message combination means 12 and message separation means 13(which separates a user identification message from a routersolicitation message and combines the former with the latter) can beimplemented by adding the solution of option 6 shown in FIG. 3 to an IPneighbor discovery message (RS/RA message) defined in RFC 2461 as shownin 2A-2C or separating the former from the latter.

FIG. 6 shows a flowchart of a method of implementing addressconfiguration for user equipment in access device 2 in an IPv6protocol-based communication network according to an embodiment of thepresent invention.

In step S101, a user solicitation message (e.g. a router solicitation(RS) message defined in RFC 2461) is received from user equipment.

In step S102, user identification information is added to the usersolicitation message. The user identification information may containrelay agent ID representing access device 1 and a port identifiercorresponding to the user equipment (or DSL).

In step S103, the user solicitation message to which the useridentification information was added is sent to a routing device (e.g.edge router).

In step S104, a router response message (e.g. a router advertisement(RA) message defined in RFC 2461) is received from the routing device,which RA message contains user identification information (may contain aport identifier only or relay agent ID and a port identifier) and aparticular address prefix corresponding to user equipment.

In step S105, the user identification information and the correspondingparticular address prefix information are separated from the routerresponse message. As described previously, the user identificationinformation at least includes a port identifier for identifying userequipment (or DSL).

In step S106, the particular address prefix information is sent via aport indicated by the port identifier to corresponding user equipment inaccordance with the user identification message.

Preferably, the access device 1 is a layer 2 access device with somelayer 3 functionalities, and more preferably, is an Ethernet accessdevice.

Preferably, the steps of combining a user identification message with arouter solicitation message and separating the former from the lattercan be implemented by adding the solution of option 6 shown in FIG. 3 toan IP neighbor discovery message (RS/RA message) defined in RFC 2461 asshown in 2A-2C or separating the former from the latter.

FIG. 7 shows a routing device 2 implementing address configuration foruser equipment 3 in an IPv6 protocol-based communication networkaccording to an embodiment of the present invention, which comprisesreception means 21, message separation means 22, allocation means 23,message combination means 24, and sending means 25.

Reception means 21 is for receiving a user solicitation message (e.g. arouter solicitation (RS) message defined in RFC 2461) from access device2, wherein the RS message contains user identification information whichmay contain relay agent ID representing access device 1 and a portidentifier corresponding to the user equipment (or DSL).

Message separation means 22 is for separating the user identificationinformation from the user solicitation message.

Allocation means 23 is for allocating a corresponding particular addressprefix (e.g. IPv6 address prefix) based on the user identificationinformation (relay agent ID and port identifier).

Message combination means 24 is for adding the user identificationinformation (may contain a port identifier only or relay agent ID and aport identifier) and the corresponding particular address prefix to arouter response message (e.g. a router advertisement (RA) messagedefined in RFC 2461).

Sending means 25 is for sending the router response message to acorresponding access device based on the relay agent ID.

Preferably, access device 1 is a layer 2 access device with some layer 3functionalities, and more preferably, is an Ethernet access device.

Preferably, message separation means 22 which separates the useridentification message from the user solicitation message and messagecombination means 24 which adds the address prefix to the routerresponse message can be implemented by adding the solution of option 6shown in FIG. 3 to an IP neighbor discovery message (RS/RA message)defined in RFC 2461 as shown in 2A-2C or separating the former from thelatter.

FIG. 8 shows a flowchart of a method of implementing addressconfiguration for user equipment 3 in routing device 2 in an IPv6protocol-based communication network, according to an embodiment of thepresent invention.

In step S201, a user solicitation message (e.g. router solicitation (RS)message defined in RFC 2461) is received from access device 2, whereinthe RS message contains user identification information which maycontain relay agent ID representing access device 1 and a portidentifier corresponding to the user equipment (or DSL).

In step S202, the user identification information is separated from theuser solicitation message.

In step S203, a corresponding particular address prefix (e.g. IPv6address prefix) is allocated based on the user identificationinformation (relay agent ID and port identifier).

In step S204, the user identification information (may contain a portidentifier only or relay agent ID and a port identifier) and theparticular address prefix are added to a router response message (e.g. arouter advertisement (RA) message defined in RFC 2461).

In step S205, the router response message is sent to a correspondingaccess device based on the relay agent ID.

Preferably, access device 1 is a layer 2 access device with some layer 3functionalities, and more preferably, is an Ethernet access device.

Preferably, step S202 of separating the user identification message fromthe user solicitation message and step S204 of adding the address prefixto the router response message can be implemented by adding the solutionof option 6 shown in FIG. 3 to an IP neighbor discovery message (RS/RAmessage) defined in RFC 2461 as shown in 2A-2C or separating the formerfrom the latter.

Compared with the prior art, the present invention allocates a dedicatedaddress prefix for each user equipment (or DSL) by adding to an RS/RAmessage user identification information for indicating user equipment,thereby achieving stateless address configuration in IPv6 service andsolving the security and scalability problem caused by applying thesolutions of the prior art to an access network directly.

The concrete embodiments of the present invention have been describedabove. It is to be understood that the present invention is not limitedto the specific embodiments. On the contrary, various variations ormodifications can be made by those skilled in the art within the scopeof the amended claims.

What is claimed is:
 1. A method for address configuration in an accessdevice in an IPv6 protocol supported communication network, the methodcomprising: receiving, at the access device, a user solicitation messagefrom user equipment; adding, at the access device, user identificationinformation identifying the user equipment to the user solicitationmessage, the user identification information including relay agentidentification of the access device and a logic port identifiercorresponding to the user equipment, to generate a solicitation messageto which the user identification information is added; sending, by theaccess device, the solicitation message to which the user identificationinformation is added; and receiving, at the access device, a firstrouter response message, the first router response message including theuser identification information and a user-specific address prefix thatis based on the user identification information.
 2. The method accordingto claim 1, further comprising: separating, at the access device, theuser-specific address prefix and the user identification informationfrom the first router response message to obtain a second routerresponse message, the second router response message including theuser-specific address prefix and excluding the user identificationinformation; and sending, by the access device, the second routerresponse message to the user equipment according to the useridentification information.
 3. The method according to claim 1, whereinthe access device is an Ethernet access device.
 4. An access device foraddress configuration for user equipment in an IPv6 protocol supportedcommunication network, the access device comprising: a first receptiondevice for receiving a user solicitation message from user equipment; amessage combination device for adding user identification informationidentifying the user equipment to the user solicitation message, togenerate a solicitation message to which the user identificationinformation is added; a first sending device for sending thesolicitation message to which the user identification information isadded, to an edge router, the user identification information includingrelay agent identification of the access device and a logic portidentifier corresponding to the user equipment; and a second receptiondevice for receiving a router response message including the useridentification information and a user-specific address prefix that isbased on the user identification information.
 5. The access deviceaccording to claim 4, characterized by further comprising: a messageseparation device configured to separate the user-specific addressprefix and the user identification information from the first routerresponse message to obtain a second router response message, the secondrouter response message including the user-specific address prefix andexcluding the user identification information; and a second sendingdevice configured to send the second router response message to the userequipment according to the user identification information.
 6. Theaccess device according to claim 4, wherein the access device is anEthernet access device.
 7. A method for address configuration in arouting device of an IPv6 protocol supported communication network, themethod comprising: receiving a user solicitation message; separatinguser identification information from the user solicitation message, theuser identification information including relay agent identification ofan access device and a logic port identifier corresponding to the userequipment; allocating a user-specific address prefix based on the useridentification information; adding the user-specific address prefix andthe user identification information to a router response message; andsending the router response message to which the user identificationinformation and the user-specific address prefix are added.
 8. Themethod according to claim 7, wherein the access device is an Ethernetaccess device.
 9. A routing device for address configuration for userequipment in an IPv6 protocol supported communication network, therouting device comprising: a reception device configured to receive auser solicitation message; a message separation device configured toseparate user identification information from the user solicitationmessage, the user identification information including relay agentidentification of an access device and a logic port identifiercorresponding to the user equipment; an allocation device configured toallocate a user-specific address prefix based on the relay agentidentification and the port identifier; a message combination deviceconfigured to add the user-specific address prefix, the relay agentidentification and the port identifier to a router response message; anda sending device configured to send the router response message to whichthe user identification information and user-specific address prefix areadded.
 10. The routing device according to claim 9, wherein the accessdevice is an Ethernet access device.